One thing to keep in mind is that you're not struggling with it if you avoid it. Struggle is a key part of learning, but that involves attempting to tackle it per the instructions (so for example, ensuring that you're designing intentional shadow shapes with their outlines first, before filling them in, rather than timidly putting down a few vague marks without specific intent). So make sure that you're not actively avoiding tackling things that you struggle with, as that is the purpose of all we do here.

As to the texture challenge, I think waiting until after Lesson 7 is fine, but if you do start at it prior to Lesson 7, the thing to keep in mind is that it is not something you should be doing all at once, unlike the box/cylinder/wheel challenges. It is something you do spread out over a long period of time, which is why in the brief material discussing it, we recommend doing it in parallel with the other lessons. This leaves plenty of room for your brain to ruminate over what little things you subconsciously pick up on from attempt to attempt, and combining them with the other spatial reasoning concepts you learn through the constructional drawings. Since Lesson 7 is pretty long and arduous, starting on it now should still give you a fair bit of room to get that kind of spacing, but if you do it after Lesson 7, be sure not to try and tackle it all at once.

In regards to doing the form intersections and organic intersections, form intersections do come up as part of Lesson 7 as well, but given that your warmups (per Lesson 0) would involve picking exercises at random from the pool of exercises you've gathered throughout the course, then I would have expected them to come up now and again there. There shouldn't be any requirement to focus your warmups specifically on them, and that would undermine other exercises that also require continued attention.

The structural issues in your wheels however are not an issue of understanding or an absence of skill. It's an absence of patience, and a tendency to act without thinking. No specific exercise is going to address this, but rather continually pushing yourself to take as much time as a task requires, and not pushing yourself to complete tasks on arbitrary timelines (allowing yourself to spread them across multiple sessions as needed) and making a point of catching yourself and reinforcing that need for patience each time you catch yourself rushing is what will help.

It's not an easy thing, especially if you're prone to giving up control of your actions to your subconscious, but that is something we talk about here in Lesson 0's material - more in the context of those students who struggle with the 50% rule, but the concept is ultimately the same. In you, is effectively a muscle that grows stronger the more you consciously exert control over your actions and choices, and grows weaker the more you abdicate that responsibility to your subconscious and instincts. In the context of the 50% rule, it being weaker can cause the anxieties associated with drawing the things that come into our mind, and having them turn out badly due to a lack of skill, to overwhelm us and create mental blocks that stop us from trying. In the context of the lesson work, where we must be hyper-intentional about the choices we make so that we can push new behaviours down into that subconscious, it causes us to slip back into relying on that auto-pilot more frequently. But the more you push back against it, the more you catch yourself as it happens, the more you strengthen that muscle and the easier it becomes. Entirely like lifting weights, that which starts off difficult and that may seem impossible, becomes easier and comes closer within your reach.